Operation Manual – Routing ProtocolH3C S7500 Series Ethernet Switches Chapter 4 OSPF Configuration4-11To do... Use the command... RemarksConfigure the networksegments in the areanetwork addresswildcard-maskRequiredBy default, an interface does notbelong to any area.Note:z The undo protocol multicast-mac enable command must be configured if Layer2/Layer 3 multicast function is enabled in the system.z In router ID selection, the priorities of the router IDs configured with the ospf[ process-id [ router-id router-id ] ] command, the router id command, and thepriorities of the router IDs automatically selected are in a descending order.z Router IDs can be re-selected. A re-selected router ID takes effect only after theOSPF process is restarted.z The ospf [ process-id [ router-id router-id ] ] command is recommended forconfiguring router IDs manually.z The ID of an OSPF process is unique.z A segment can belong to one area only and you must specify each OSPF interfaceto belong to a particular area.4.4 OSPF Area Attribute ConfigurationArea partition in OSPF reduces the number of LSAs in the network and enhancesOSPF scalability. To further reduce routing table size and the number of LSAs in somenon-backbone areas on the edge of the AS, you can configure these areas as stubareas.A stub area cannot import any external route. For this reason the concept of NSSAarea is introduced. Type7 LSAs can be advertised in an NSSA area. Type7 LSAs aregenerated by ASBRs of the NSSA area, and will be transformed into AS-externalLSAs whey reaching ABRs in the NSSA area, which will then be advertised to otherareas.After area partition, the OSPF route updates between non-backbone areas areexchanged by way of the backbone area. Therefore, OSPF requires that all thenon-backbone areas should keep connectivity with the backbone area and thebackbone area must keep connectivity in itself.If the physical connectivity cannot be ensured due to various restrictions, you canconfigure OSPF virtual links to satisfy this requirement.
